The zebrafish is an attractive, easily accessible animal model to study the genetics of embryogenesis. Already, chemical mutagenesis screens have generated more than one thousand mutants that have defects in most developmental processes. To fully realize the potential of this system for gene function and regulation studies, we propose to establish additional transgenic technologies and resources that will facilitate the genetic analysis of vertebrate development using zebrafish. We have developed a high throughput method for modifying bacterial artificial chromosomes (BAC) as transgenic constructs. In this proposal, we plan to generate 500-600 GFP-marked BAC constructs containing tissue/cell-specific regulatory sequences and make them freely available to zebrafish community. As a service, researchers can send in their BAC clones and we will finish modifying them with GFP or a transgene of interest in two-three weeks. This has already been effectively done for a number of labs now. Secondly, we will continue to develop better transgenic technology for zebrafish, including inducible transgenic system and inducible conditional alleles by Cre-loxP. All resources generated from this support will be deposited to the International Zebrafish Stock Center for community access. With these sophisticated technologies established in zebrafish, our ability to analyze gene expression and function in vivo will be greatly enhanced. [unreadable] [unreadable]